The February 1995 issue of APIS says:
 
It is now official!  Resistance to fluvalinate, the active
ingredient in ApistanR, has been found in Varroa mites.  This
was published in the February 1995 issue of Bee Culture (Vol.
123, No. 2, pp. 80-81) in "9th International Congress of
Acarology," by E. Sugden, K. Williams and D. Sammataro.
According to these authors: "The most ominous report came from
Dr. Roberto Nannelli of Italy.  He has found areas where
Varroa mites are over 90 percent fluvalinate-resistant, and
his claims have been confirmed by German scientists."
 
Oscar Coindreau, representative of Sandoz Agro, the company
that makes ApistanR, also verified this report at the recent
meeting of the American Beekeeping Federation in Austin, TX.
He indicated that resistance was patchy in Italy, but in
certain areas, ApistanR provided no control.
...
All investigators indicate that the cause of this resistance
is  not ApistanR, but beekeepers' misuse of other formulations
of fluvalinate.  In Europe the product is called KlartanR and
in the United States, MavrikR.
 
in the United States, MavrikR.